* Added a command ‘nix-store --verify-paths PATHS’ to check whether

the contents of any of the given store paths have been modified.
  E.g.

    $ nix-store --verify-path $(nix-store -qR /var/run/current-system)
    path `/nix/store/m2smyiwbxidlprfxfz4rjlvz2c3mg58y-etc' was modified! expected hash `fc87e271c5fdf179b47939b08ad13440493805584b35e3014109d04d8436e7b8', got `20f1a47281b3c0cbe299ce47ad5ca7340b20ab34246426915fce0ee9116483aa'

  All paths are checked; the exit code is 1 if any path has been
  modified, 0 otherwise.

src/libmain/shared.hh

@@ -53,6 +53,9 @@ struct RemoveTempRoots
     ~RemoveTempRoots();    
 };
 
+/* Exit code of the program. */
+extern int exitCode;
+
 }